3,114 research outputs found
Coupled forward-backward trajectory approach for non-equilibrium electron-ion dynamics
We introduce a simple ansatz for the wavefunction of a many-body system based
on coupled forward and backward-propagating semiclassical trajectories. This
method is primarily aimed at, but not limited to, treating nonequilibrium
dynamics in electron-phonon systems. The time-evolution of the system is
obtained from the Euler-Lagrange variational principle, and we show that this
ansatz yields Ehrenfest mean field theory in the limit that the forward and
backward trajectories are orthogonal, and in the limit that they coalesce. We
investigate accuracy and performance of this method by simulating electronic
relaxation in the spin-boson model and the Holstein model. Although this method
involves only pairs of semiclassical trajectories, it shows a substantial
improvement over mean field theory, capturing quantum coherence of nuclear
dynamics as well as electron-nuclear correlations. This improvement is
particularly evident in nonadiabatic systems, where the accuracy of this
coupled trajectory method extends well beyond the perturbative electron-phonon
coupling regime. This approach thus provides an attractive route forward to the
ab-initio description of relaxation processes, such as thermalization, in
condensed phase systems
Rebuilding our Neighborhoods: Improving New York State Housing Policy to Better Meet Upstate Needs
New York faces a wide variety of housing challenges. While in the New York City region, where the population is growing, availability and affordability are the most pressing concerns, upstate regions have a different set of problems stemming from population loss, housing vacancy, abandonment, and deterioration. To address the full range of issues, state housing policy needs a variety of tools in its tool box. This policy brief discusses four ways that state housing policy can better address the needs of upstate regions such as Buffalo: Support holistic neighborhood revitalization, using Buffalo’s award-winning Green Development Zone as a model; Restore and enhance funding streams for small projects and housing repairs; Adjust New York’s Low Income Housing Tax Credit Qualified Allocation Plan to better address upstate needs; and Revise the DHCR Design Handbook to better facilitate rehabilitation projects
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